Iranian dissidents have long suspected that the country's Islamist regime has used the cover of its not-so-covert war with Israel to crack down on internal opponents, and that a leading Iranian nuclear scientist whose death was blamed on Mossad might really have been killed by his own government.

Now an opposition blogger based in London says that discrepancies in the recent trial and execution of the "Israeli spy" officially charged with killing scientist Masoud Ali Mohammadi are yet more evidence that Iranian intelligence agents may have been the real assassins.

Mohammadi, a nuclear physicist, died in January 2010 when a motorcycle parked outside his house was detonated by remote control when he walked past.

A half dozen scientists and officials linked to the nation's nuclear and long-range missile programs have died under suspicious circumstances since 2010, deaths the Iranian regime usually blames on Israel, the U.S., and the U.K. When Mohammadi died, the regime immediately blamed his murder on a "triangle of wickedness," meaning the U.S., Israel and their "hired agents."

"Zionists did it," said President Mahmoud Ahmadinejad. "They hate us and they don't want us to progress." Ali Larjani, chairman of the Iranian parliament, said the government had "clear information that the intelligence regime of the Zionist regime and the CIA wanted to implement terrorist acts."

But Western intelligence agencies had conflicting information about whether Mohammadi, a particle physicist, was really contributing to the nuclear program. Iranian dissidents. Meanwhile, said Mohammadi had been killed by the regime because he was a supporter of reformist candidate Mir Hossein Mousavi, whom many believe actually won the 2009 Iranian presidential election before vote-tampering handed the victory to Ahmadinejad. A German-based opposition group released a photo of an alleged Arab hitman who had supposedly carried out Mohammadi's assassination on regime orders.

At Mohammadi's funeral, hundreds of regime loyalists waving anti-Israel banners packed the procession, where they clashed with supporters of Mousavi's Green Movement.

More than two years later, on May 15, 2012, the Iranian government executed 24-year-old Majid Jamali Fashi, who had been convicted of assassinating Mohammadi.

Iranian authorities claimed that Fashi, 24, was recruited and trained by Mossad and was paid $120,000 to kill Mohammadi. In January 2011, Iranian media had broadcast Fashi's confession, in which he said he "received different training including chasing, running, counter-chasing and techniques for planting bombs in a car" while in Tel Aviv. Fashi also confessed to receiving forged travel documents in Azerbaijan to travel to Israel, Iran's Press TV reported.

In a blog post Monday, however, London-based dissident Potkin Azarmehr pointed out that the Israeli passport displayed by Iranian television was stamped 2003, when Fashi was 15 years old, but bore the photo of a hirsute man in his 20s who is not looking directly into the camera. "No passport will be issued with such a picture, anywhere in the world," wrote Azarmehr. "You need a headshot where you are open-eyed AND looking into the camera."

Azarmehr, whose work has been published in the Guardian and the Wall Street Journal, believes that Fashi is not a Mossad agent and may never have been executed. In earlier posts, Azarmehr claimed that Fashi showed no fear in a video allegedly recorded right before his execution, and that the only official photo taken of him after his hanging shows him from far away.

Other news outlets that have reported Azarmehr's suspicions, however, have focused on the alleged forgery of the passport. The Dubai-based news channel al-Arabiya claims that the passport displayed on Iranian television has a misplaced passport number and design features that indicate it dates from the 1990s. One blogger found a facsimile of an Israeli passport with the same dates and city of origin on Wikipedia and alleges that Fashi's passport is simply a crude copy. All the blacked-out areas on the Wikipedia image, seen here, appear as blanks on Fashi's alleged passport.

The U.S. and the U.K. have denied any involvement in the deaths of Iranian nuclear scientists, while the Israeli government has declined to comment.

Reporting by the New Yorker and NBC has linked the hits on Iranian nuclear scientists to an Iranian expatriate group often identified as MEK, a group allegedly trained in the U.S. and supported by Israel.

Iran Uncovers CIA Spy Operations

In the past, U.S. officials have conceded that Iran has had success in identifying Western agents operating inside the country.

In 2011, Iranian intelligence minister Heidar Moslehi announced in May 2011 that more than 30 U.S. and Israeli spies had been discovered and an Iranian television program, which acts as a front for Iran's government, showed images of internet sites used by the U.S. for secret communication with the spies.

U.S. officials told ABC News that much of what was broadcast was, in fact, true. U.S. officials said the Iranian television program showed pictures of people who were not U.S. assets, but the program's video of the websites used by the CIA was accurate.

The number of CIA assets in Iran who may have been compromised could be in the dozens, according to one current and one former U.S. intelligence official.

A U.S. official speaking for the record but without attribution gave grudging credit to Iran for its efforts to detect and expose U.S. and Israeli espionage.

"Collecting sensitive information on adversaries who are aggressively trying to uncover spies in their midst will always be fraught with risk," the U.S. official said.